Porosity and Ion Diffusivity of Latex-Modified Cement

1989 ◽  
Vol 176 ◽  
Author(s):  
Takashi Nishi ◽  
Osamu Kuriyama ◽  
Masami Matsuda ◽  
Koichi Chino ◽  
Makoto Kikuchi
Keyword(s):  
Pore Water ◽  
Cement Paste ◽  
Nuclear Power ◽  
Power Plants ◽  
Total Porosity ◽  
Bulk Water ◽  
Hardened Cement ◽  
Cement Pastes ◽  
Water Proof ◽  
Cs Ions

ABSTRACTLatex-modified Portland cement, which would be expected to have low permeability and ion diffusivity, was studied for possible application as a solidification agent for radioactive wastes generated from nuclear power plants. In order to predict the leaching ratio of radionuclides from the cementitious waste forms, the effect of water and latex content in the fresh cement paste on total porosity and ion diffusivity of hardened paste was quantitatively estimated.Total porosity of hardened cement paste decreased with the reduction of water content in the fresh paste and it was also reduced by latex addition. This latter effect could be attributed to the latex emulsion forming a water-proof film and filling the capillary pores. Also Cs ions diffusivity, which is the ratio of the diffusion coefficient in pore water to that in bulk water, showed an exponential correlation with total porosity for both cement materials. An empirical equation, expressing ion diffusivity as a function of total porosity, was derived from the consideration that the water constrictivity in this porous medium could cause an increase of the apparent viscosity of pore water. These results suggested a possibility that the transport behavior of radionuclides through the cementitious matrix could be estimated from the mixing parameters of the original cement pastes.

scholarly journals The Influence of Fluidized Bed Combustion Fly Ash on the Phase Composition and Microstructure of Cement Paste

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2838
Author(s):  
Michał A. Glinicki ◽  
Daria Jóźwiak-Niedźwiedzka ◽  
Mariusz Dąbrowski
Keyword(s):  
Phase Composition ◽  
Fly Ash ◽  
Fluidized Bed ◽  
Cement Paste ◽  
Power Plants ◽  
Circulating Fluidized Bed ◽  
Thermal Analyses ◽  
Hardened Cement ◽  
Fluidized Bed Combustion ◽  
Cement Pastes

Fly ashes from coal combustion in circulating fluidized bed boilers in three power plants were tested as a potential additive to cement binder in concrete. The phase composition and microstructure of cement pastes containing fluidized bed fly ash was studied. The fractions of cement substitution with fluidized bed fly ash were 20% and 30% by weight. X-ray diffraction (XRD) tests and thermal analyses (derivative thermogravimetry (DTG), differential thermal analysis (DTA) and thermogravimetry (TG)) were performed on ash specimens and on hardened cement paste specimens matured in water for up to 400 days. Quantitative evaluation of the phase composition as a function of fluidized bed fly ash content revealed significant changes in portlandite content and only moderate changes in the content of ettringite.

The Influence of Pore-Strucrure on the Campressive Strength of Hardened Cement Paste

1984 ◽  
Vol 42 ◽  
Author(s):  
Huang Yiun-Yuan ◽  
Ding Wei ◽  
Lu Ping
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Pore Structure ◽  
Cement Paste ◽  
Total Porosity ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
New Information ◽  
The Relationship ◽  
Empirical Constants

AbstractThe pore-structure strongly influences the carpressive strength of hardened cement paste (hcp) and other porous materials, as well as other mechanical properties. The simplest but most currently used expression representing the relationship between the pore-structure and compressive strength is fram Balshin: σ = σ0 (l-P)A, in which only the total porosity P is involved as a single parameter and σ0 and A are empirical constants. The influence of pore size distribution and pore shapes etc. are not considered.The authors introduce second parameter w - the factor of relative specific surface area of the pores other than the total porosity P into consideration and a new expression is proposed:σc=K11-p/1+2p(K2(1-p))K3w+K4 all the constants K1 - K4 can be determined experimentally. By using of this expression the new information relating the influence of pore-structure on the caopressive strength of hcp can be predicted.

Corrosion of Hardened Cement Paste by NH4NO3 and Acetic and Formic Acids

1988 ◽  
Vol 137 ◽  
Author(s):  
Adolf Bajza
Keyword(s):  
Time Use ◽  
Mercury Intrusion Porosimetry ◽  
Total Porosity ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Cement Pastes ◽  
Blended Cements ◽  
Water To Cement Ratio ◽  
Hardened Cement Pastes

AbstractEffects of NH4NO3, CH3COOH and HCOOH solutions on the pore structure and other properties of hardened cement pastes made out of portland, slag, and fly ash cements at different water-to-cement ratios are discussed.Total porosity and the volume of pores detectable by mercury intrusion porosimetry (MIP) increased with increasing water-to-cement ratio, concentration of aggressive solution, and time of immersion. The weight, bulk density, and compressive strenath of the samples decreased at the same time. Use of blended cements did not result in improvement of the long-term durability of the samples. The degradation of the cement pastes increased from NH4NO3 to CH3COOH to HCOOH.

scholarly journals Performance of ANN in Predicting Internal Bonding of Cement Particleboard Manufactured from Giant Reed and Bagasse

2021 ◽  
Vol 72 (3) ◽  
pp. 255-271
Author(s):  
Morteza Nazerian ◽  
Hossin Assadolahpoor Nanaii ◽  
Elham Vatankhah ◽  
Mojtaba Koosha
Keyword(s):  
Cement Paste ◽  
Bonding Strength ◽  
Microstructural Analysis ◽  
Giant Reed ◽  
Hardened Cement ◽  
Data Sets ◽  
Internal Bonding ◽  
Cement Pastes ◽  
Coeffi Cients ◽  
Artificial Neural Network Ann

The present article investigates the microstructure of the cement matrices and the products of cement hydration by means of scanning electron microscopy, Fourier transform infrared spectroscopy and X-Ray diffraction. Then, the internal bonding strength (IB) is measured for the mixtures containing various amounts of nanosilica (NS), reed and bagasse particles. Finally, an Artificial Neural Network (ANN) is trained to reproduce these experimental results. The results show that the hardened cement paste including NS features the highest level of C-S-H. However, it has a lower level of C-S-H polymerization if reed or bagasse particles are applied. A relatively new dense microstructural degree is considered in the cement pastes containing NS, and a lower agglomeration is observed in the samples including reed or bagasse particles with NS. According to the microstructural analysis, the addition of NS to the samples containing reed or bagasse particles increases the unhydrated amount of C2S and C3S in the cement paste due to the decrease in the water needed for fully hydrated cement grains through portlandite (Ca(OH)2), C-S-H and ettringite increase. Besides, it is shown that the ANN prediction model is a useful, reliable and quite effective tool for modeling IB of cement-bonded particleboard (CBPB). It is indicated that the mean absolute percentage errors (MAPE) are 1.98 % and 1.45 % in the prediction of the IB values for the training and testing datasets, respectively. The determination coeffi cients (R2) of the training and testing data sets are 0.972 and 0.997 in the prediction of the bonding strength by ANN, respectively.

OPTIMAL CRITERIA OF ALGERIAN BLENDED CEMENT USING LIMESTONE FINES/ALŽYRIETIŠKAS MIŠRUSIS CEMENTAS SU MALTU KALKAKMENIU

2008 ◽  
Vol 14 (4) ◽  
pp. 269-275 ◽  
Author(s):  
Z’hor Guemmadi ◽  
Musa Resheidat ◽  
Hacéne Houari ◽  
Belkacem Toumi
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Blended Cement ◽  
Total Porosity ◽  
Hardened Cement ◽  
Compact Structure ◽  
Limestone Filler ◽  
Cement Pastes ◽  
Limestone Fines ◽  
Hardened Cement Pastes

The effect of substitution of Portland cement by limestone up to 40% as well as its fineness on the physico‐mechanical properties of fresh and hardened cement pastes is studied. The binder was prepared by substitution of cement by limestone filler. Fillers were chosen of various particle sizes and with percentages from 5 to 40. Test results revealed that the replacement of Portland cement by the finest filler of limestone slightly decreases the consistency and the setting times (initial and final). The total porosity decreases and accordingly the compressive strength is improved with the content and fines of limestone. Although limestone has a little accelerating effect on the hydration process of Portland cement, but acts only as a filler reducing the porosity due to its compact structure, in which the compressive strength of the hardened cement paste is enhanced. The XRD and DTA analyses of samples cured up to 28 days showed that this amelioration is due to formation of new hydrated compounds. It is concluded that an addition of finely ground limestone filler only up to 15% gives a better strength. Santrauka Tirtos šviežios ir sukietėjusios cementinės tešlos, kurioje iki 40 % cemento pakeista įvairaus smulkumo maltu kalkakmeniu, savybės. Rišiklis buvo paruoštas dalį cemento pakeitus maltu kalkakmenio užpildu. Užpildo dalelės buvo įvairaus dydžio, o jų kiekis buvo keičiamas nuo 5 % iki 40 %. Tyrimai parodė, kad priedas leidžia sumažinti vandens kiekį, reikalingą tos pačios konsistencijos mišiniui gauti, taip pat cemento rišimosi pradžiai ir pabaigai paankstinti. Sumažėja cementinio akmens suminis poringumas ir atitinkamai padidėja stipris gniuždant cementinio akmens, kuriame yra kalkakmenio priedų. Nors kalkakmenio priedas nedaug pagreitina portlandcemenčio hidratacijos procesą, tačiau veikia kaip užpildas, sutankinantis struktūrą, dėl to labai padidėja sukietėjusio cementinio akmens stipris gniuždant. Bandinių, išlaikytų 28 dienas, rentgenostruktūrinė ir diferencinė terminė analizė parodė, kad pagerėjimas yra dėl susidariusių naujadarų. Apibendrinant galima teigti, kad 15 % malto kalkakmenio priedas turi didžiausią įtaką stiprumo rezultatams.

scholarly journals Physical and Chemo/Mechanical behaviors of fly ash and silica fume belite cement pastes- Part I

NanoNEXT ◽  
2021 ◽  
pp. 1-15
Author(s):  
Darweesh H.H.M
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Total Porosity ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Heat Of Hydration ◽  
Hardened Cement ◽  
Cement Pastes ◽  
Belite Cement

Physical, chemical and mechanical properties of high belite cement (HBC) blended with high pulverized fly ash (HPFA) with stable ratio of silica fume (SF) in comparison with Portland cement (OPC) were investigated. Results showed that the water of consistency and setting times (Initial and final) tended to increase with the increase of HPFA content. The bulk density and compressive strength were also improved and enhanced with the increase of HPFS content at all hydration times, but only up to 15 % HPFA, and then decreased with further increase.  However, the total porosity slightly decreased, but started to increase with further increase of >15 % HPFA. The free lime content of the pure OPC and HBC gradually were increased as the hydration times progressed up to 90 days, while those of blended cements increased only up to 7 days and then decreased onward. The results were confirmed by measuring the heat of hydration and ultrasonic pulse velocity for the optimum cement pastes comparing with those of both OPC and HBC. The heat of hydration of the optimum cement pastes was decreased at all hydration times and become lower than those of OPC and HBC. The ultrasonic pulse velocity test (USPV) proved that the uniformity and quality of the matrix of the hardened cement pastes are good with no cracks.

scholarly journals Difference between Internal and External Hydration of Hardened Cement Paste under Microwave Curing

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Guoshun Yan ◽  
Jiazheng Li ◽  
Yuqiang Lin ◽  
Xia Chen
Keyword(s):  
Cement Paste ◽  
Outer Part ◽  
Total Porosity ◽  
Fracture Morphology ◽  
Hardened Cement ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
Hydration Degree ◽  
Microwave Curing ◽  
The Difference

In order to investigate the difference between internal and external hydration of hardened cement paste under microwave curing, a comparative study on the hydration products, hydration degree, fracture morphology, and pore structure between the inner part and outer part of hardened cement paste (Φ120 mm × 120 mm) under microwave curing was carried out by XRD-Rietveld refinement, TG-DSC, SEM, and MIP methods. The results show that the total hydration degree of the inner part is lower at early ages, but with the hydration, there is little difference in the hydration degree between inner and outer parts at later ages. Apart from granular AFt crystal formed in the inner part of hardened cement paste, there is little difference in the fracture morphology between internal and external hydration. The total porosity of the outer part is lower than that of the inner part.

An Investigation Of A High Speed Shear Mixer On Selected Pastes And Mortars

1988 ◽  
Vol 137 ◽  
Author(s):  
M. L. Brown ◽  
W. B. Ledbetter ◽  
H. M. Jennings
Keyword(s):  
Cement Paste ◽  
High Speed ◽  
Initial Study ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Cement Pastes ◽  
Shear Mixing ◽  
Paddle Mixer

AbstractThe influence of shear mixing on selected properties of cement pastes and mortars was investigated by preparing specimens using an ordinary paddle mixer and a high speed shear mixer. The results appear to indicate that shear mixing influences the bond between paste and aggregate, particularily at low water:cement ratios. The properties of hardened cement paste did not change markedly as a result of high speed shear mixing used in this initial study.

The Relationship between the Strength and the Pore Structures of Cement Paste with Mineral Admixtures

2011 ◽  
Vol 250-253 ◽  
pp. 104-108 ◽  
Author(s):  
Yue Li ◽  
Jun Ling Bao ◽  
Chun E Sui ◽  
Xiu Li Du
Keyword(s):  
Compressive Strength ◽  
Pore Structure ◽  
Cement Paste ◽  
Mapping Function ◽  
Mineral Admixtures ◽  
Hardened Cement ◽  
Cement Pastes ◽  
Binder Ratio ◽  
Water To Binder Ratio ◽  
The Relationship

This paper presents the effects of mineral admixtures and the water to binder ratio (W/B) on the tensile and compressive strength and micro pore structure of hardened cement pastes. The test results show that: with the water to binder ratio increasing, the tensile and compressive strength of cement paste with different mineral admixtures will decrease, air content and mean pore diameter will decrease and the cement paste with the ground blast furnace slag is the lowest. The artificial neural network based on its nonlinear mapping function can fit the relationship between strength and pore structure more accurate than an empirical formula.

scholarly journals On Phase Identification of Hardened Cement Pastes by Combined Nanoindentation and Mercury Intrusion Method

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3349
Author(s):  
Jingwei Ying ◽  
Xiangxin Zhang ◽  
Zhijun Jiang ◽  
Yijie Huang
Keyword(s):  
Mechanical Properties ◽  
Pore Structure ◽  
Cement Paste ◽  
Phase Distribution ◽  
Gaussian Mixture ◽  
Hardened Cement ◽  
Phase Identification ◽  
Hardened Cement Paste ◽  
Cement Pastes ◽  
Mercury Intrusion

The micro-mechanical properties of hardened cement paste can be obtained by nanoindentation. Phases at different locations can generally be determined by using the Gaussian mixture model (GMM) method and the K-means clustering (KM) method. However, there are differences between analysis methods. In this study, pore structure and porosity of hardened cement paste aged three, seven, and 28 days were obtained by mercury intrusion porosimetry (MIP), and their micro-mechanical properties were obtained by the nanoindentation method. A new method, GMM-MIP and KM-MIP, was proposed to determine the phase of hardened cement paste based on the pore structure and nanoindentation results. The results show that GMM-MIP and KM-MIP methods are more reasonable than GMM and KM methods in determining the phase of hardened cement paste. GMM-MIP can be used to obtain reasonable phase distribution. If the micro-mechanical properties of each phase in hardened cement paste do not satisfy the normal distribution, the GMM method has significant defects.

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